ATmega64C1 Automotive Atmel Corporation, ATmega64C1 Automotive Datasheet - Page 238

• Manufacturer Part Number: ATmega64C1 Automotive
• Manufacturer: Atmel Corporation

Specifications of ATmega64C1 Automotive

• Flash (kbytes): 64 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 27
• Ext Interrupts: 27
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Uart: 1
• Can: 1
• Lin: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 11
• Adc Resolution (bits): 10
• Adc Speed (ksps): 125
• Analog Comparators: 4
• Resistive Touch Screen: No
• Dac Channels: 1
• Dac Resolution (bits): 10
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 4
• Eeprom (bytes): 2048
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 150
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 4
• Input Capture Channels: 1
• Pwm Channels: 4
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

18.6.2
18.6.3
18.6.4
238
Atmel ATmega16/32/64/M1/C1
Analog Noise Canceling Techniques
Offset Compensation Schemes
ADC Accuracy Definitions
If differential gain channels are used, the input circuitry looks somewhat different, although
source impedances of a few hundred k or less is recommended.
Signal components higher than the Nyquist frequency (f
kind of channels, to avoid distortion from unpredictable signal convolution. The user is advised
to remove high frequency components with a low-pass filter before applying the signals as
inputs to the ADC.
Figure 18-8. Analog Input Circuitry
Digital circuitry inside and outside the device generates EMI which might affect the accuracy of
analog measurements. If conversion accuracy is critical, the noise level can be reduced by
applying the following techniques:
The gain stage has a built-in offset cancellation circuitry that nulls the offset of differential mea-
surements as much as possible. The remaining offset in the analog path can be measured
directly by shortening both differential inputs using the AMPxIS bit with both inputs uncon-
nected.
“Amplifier 1 Control and Status register – AMP1CSR” on page
trol and Status register – AMP1CSR” on page
subtracted in software from the measurement results. Using this kind of software based offset
correction, offset on any channel can be reduced below one LSB.
An n-bit single-ended ADC converts a voltage linearly between GND and V
(LSBs). The lowest code is read as 0, and the highest code is read as 2
Several parameters describe the deviation from the ideal behavior:
1. Keep analog signal paths as short as possible. Make sure analog tracks run over the
2. The AVCC pin on the device should be connected to the digital VCC supply voltage
3. Use the ADC noise canceler function to reduce induced noise from the CPU.
4. If any ADC port pins (PB[7:2], PC[7:4], PD[6:4], PE[2]) are used as digital outputs, it
• Offset: The deviation of the first transition (0x000 to 0x001) compared to the ideal transition
(at 0.5 LSB). Ideal value: 0 LSB.
analog ground plane, and keep them well away from high-speed switching digital
tracks.
via an RC network (R = 10 max, C = 100 nF).
is essential that these do not switch while a conversion is in progress.
(See “Amplifier 0 Control and Status register – AMP0CSR” on page
ADCn
I
IH
I
IL
1..100 k
255.). This offset residue can be then
ADC
/2) should not be present for either
C
255.and
S/H
= 14 pF
V
n
CC
See “Amplifier 1 Con-
-1.
/2
REF
7647G–AVR–09/11
in 2
254.,
n
steps
See